Index: src/wp-includes/js/tinymce/plugins/wordpress/plugin.js
===================================================================
--- src/wp-includes/js/tinymce/plugins/wordpress/plugin.js	(revision 33585)
+++ src/wp-includes/js/tinymce/plugins/wordpress/plugin.js	(working copy)
@@ -702,7 +702,14 @@
 					scrollY = window.pageYOffset || document.documentElement.scrollTop,
 					windowWidth = window.innerWidth,
 					windowHeight = window.innerHeight,
-					iframeRect = mceIframe.getBoundingClientRect(),
+					iframeRect = mceIframe ? mceIframe.getBoundingClientRect() : {
+						top: 0,
+						right: windowWidth,
+						bottom: windowHeight,
+						left: 0,
+						width: windowWidth,
+						height: windowHeight
+					},
 					toolbar = this.getEl(),
 					toolbarWidth = toolbar.offsetWidth,
 					toolbarHeight = toolbar.offsetHeight,